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(CBS) — There’s no question Ronald Johnson was running from Chicago Police in October 2014, before he was shot dead in the back by an officer.

But did Johnson, 25, have a gun?

Three years later, that’s the question still swirling around his death.

Anita Alvarez, the Cook County state’s attorney at the time, declined to criminally charge the officer who shot Johnson. The reason, she said in a nationally televised press conference in December 2015, was because evidence showed Johnson was armed.

That evidence included grainy police dashboard video, which had been sent to the FBI’s Regional Computer Forensics Laboratory to be enhanced.

Alvarez said the enhanced video appeared to show Johnson holding a gun.